Not once in the 59 pages that constitute Supreme Court Chief Justice John Roberts’s lead opinion in National Federation of Independent Business v. Sebelius does he use the word “integrity.” Even so, in the days since the individual mandate was upheld as a tax, concern for the “integrity” or “legitimacy” or “reputation” of the Roberts Court has become the most accepted explanation for why the chief justice ruled as he did.

Thus Reuters, which tells us that Justice Roberts was “trying to preserve the integrity of the judiciary in polarized Washington.” Or the New York Times, where Tom Friedman lauds the chief justice for “a simple noble leadership impulse at a critical juncture in our history—to preserve the legitimacy of the Supreme Court.” The Washington Post’s Charles Krauthammer agrees with this motivation, speculating that had Justice Roberts “been just an associate justice, and not the chief” he might well have voted otherwise.

If Mr. Krauthammer is correct, it raises a disquieting question. During Justice Roberts’s confirmation hearings back in 2005, he described judges as umpires whose job it is to call balls and strikes as he sees them. The idea that he might have voted otherwise if he were not chief justice suggests that a “strike” was changed to a “ball” because of concerns for how the straight call would be perceived.